The subject matter disclosed herein relates to gas turbine engines and, more particularly, to temperature and performance management therein.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gas that flows downstream through one or more turbine stages. A turbine stage includes a stationary nozzle having stator vanes that guide the combustion gas through a downstream row of turbine rotor blades. The blades extend radially outwardly from a supporting rotor that is powered by extracting energy from the gas.
A first stage turbine nozzle receives hot combustion gas from the combustor and directs it to the first stage turbine rotor blades for extraction of energy therefrom. A second stage turbine nozzle may be disposed downstream from the first stage turbine rotor blades, and is followed by a row of second stage turbine rotor blades that extract additional energy from the combustion gas. Additional stages of turbine nozzles and turbine rotor blades may be disposed downstream from the second stage turbine rotor blades.
As energy is extracted from the combustion gas, the temperature of the gas is correspondingly reduced. However, since the gas temperature is relatively high, the turbine stages are typically cooled by a coolant such as compressed air diverted from the compressor through the hollow vane and blade airfoils for cooling various internal components of the turbine. Since the cooling air is diverted from use by the combustor, the amount of extracted cooling air has a direct influence on the overall efficiency of the engine. It is therefore desired to improve the efficiency with which the cooling air is utilized to improve the overall efficiency of the turbine engine.
The quantity of cooling air required is dependant not only on the temperature of the combustion gas but on the integrity of the various seals which are disposed between rotating and stationary components of the turbine. Thermal expansion and contraction of the rotor and blades may vary from the thermal expansion of the stationary nozzles and the turbine housing thereby challenging the integrity of the seals. In some cases the seals may be compromised causing excess cooling air to pass into the turbine mainstream gas flow resulting in excess diversion of compressor air translating directly to lower than desired turbine efficiency.
It is therefore desired to provide a gas turbine engine having improved sealing of gas turbine stationary to rotating component interfaces.